1. Field of the Invention
The present invention relates to medical devices, and more particularly, to a device that provides an improved method for vascular access.
2. Description of Related Art
Providing frequent, direct, vascular access has become a necessity for many medical procedures including hemodialysis, chemotherapy, various tests requiring frequent blood draws and treatments requiring frequent intravenous administration of drugs. Many vascular access devices have been developed to meet this need. Often the devices are permanently inserted into the patient, but such devices have experienced a variety of problems. For example, the arteriovenous shunt includes a length of silicone rubber tubing bearing catheter tips at each end that are respectively inserted into an artery and a vein below the skin while the remaining tubing extends beyond the skin surface. This design is plagued by infection and clotting problems at the sites where the tubing passes through the skin surface. External shunts further pose an inconvenience to the patient because of the extra care that is required to avoid snagging the exposed tubing which could result in injury to the skin and to dislodging the device.
Another method of vascular access utilizes a subcutaneous autologous arteriovenous fistula that is formed by suturing a native artery to a native vein to create a high volume of blood flow in the vein. Arterial pressure causes contiguous veins to dilate and provide sites for venipuncture. However, such a fistula may not be used for several weeks after formation because significant time is required for the walls of the dilated vein to thicken sufficiently. In addition, the required, repeated needle punctures eventually weaken and destroy the arterialized vein, which, to begin with, is subject to abnormal pressurization and is particularly susceptible to collapse.
As alternatives, expanded polytetrafluoroethylene (ePTFE) bridge grafts and dual lumen venous catheters have been developed. The ePTFE bridge graft creates a loop between an artery and a vein, by suturing one end of the graft to an artery and the other end to a vein, but this device is prone to complications such as thrombosis, infection, and infiltration of scar-forming cells. After insertion, the ePTFE graft must be allowed to mature or heal prior to needle puncture, because ePTFE grafts are highly porous. After sufficient healing, surrounding body tissues grow into the walls of the ePTFE graft to provide a limited ability to self-seal. This healing process takes approximately two weeks in most patients. Failure to allow the ePTFE graft to mature or heal often results in hematoma formation, false aneurysm, leaking of blood from the needle puncture site, and/or early fistula failure. Perhaps the most significant complication, though, is neointimal hyperplasia that often occurs near the venous anastomosis and eventually ail leads to thrombosis of the graft.
With the dual lumen venous catheter, the catheter is percutaneously inserted into a central vein. Numerous complications occur with this method due to the lack of a continuous blood flow such as with the ePTFE bridge graft. These complications may include poor flow rates due to kinking or recurrent thrombosis secondary to stasis of blood in the lumen and build up of fibrinous debris at the venous end. Also, as with the external shunt described above, infection at the entry site at the skin may occur and extra care is required to avoid injury or dislodging the tubing.
Shunt devices are also known that avoid percutaneous needle punctures by providing a skin level port with connections to an artery and a vein through ePTFE tubing. These devices, as above, present the risk of infection at the skin surface and require extra care. Also, discontinuities of the blood flow path often cause a buildup of clotted blood that may restrict or ultimately seal off the flow of blood therethrough, resulting in thrombosis.
Accordingly, it would be desirable to provide a vascular access device having superior patency rates along with minimal complications in its use. The device would avoid skin surface infections, provide continuous, strong, blood flow rates to prevent thrombosis, and, minimize damage to the vascular system and associated problems such as hyperplasia. Furthermore, the device would provide immediate, easy, needle access for long-term vascular access, which is required for various medical procedures such as hemodialysis and frequent blood draws.